/*
 * Copyright (c) 1996, 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.io;


/**
 * Piped character-output streams.
 *
 * @author Mark Reinhold
 * @since JDK1.1
 */

public class PipedWriter extends Writer {

  /* REMIND: identification of the read and write sides needs to be
     more sophisticated.  Either using thread groups (but what about
     pipes within a thread?) or using finalization (but it may be a
     long time until the next GC). */
  private PipedReader sink;

  /* This flag records the open status of this particular writer. It
   * is independent of the status flags defined in PipedReader. It is
   * used to do a sanity check on connect.
   */
  private boolean closed = false;

  /**
   * Creates a piped writer connected to the specified piped
   * reader. Data characters written to this stream will then be
   * available as input from <code>snk</code>.
   *
   * @param snk The piped reader to connect to.
   * @throws IOException if an I/O error occurs.
   */
  public PipedWriter(PipedReader snk) throws IOException {
    connect(snk);
  }

  /**
   * Creates a piped writer that is not yet connected to a
   * piped reader. It must be connected to a piped reader,
   * either by the receiver or the sender, before being used.
   *
   * @see java.io.PipedReader#connect(java.io.PipedWriter)
   * @see java.io.PipedWriter#connect(java.io.PipedReader)
   */
  public PipedWriter() {
  }

  /**
   * Connects this piped writer to a receiver. If this object
   * is already connected to some other piped reader, an
   * <code>IOException</code> is thrown.
   * <p>
   * If <code>snk</code> is an unconnected piped reader and
   * <code>src</code> is an unconnected piped writer, they may
   * be connected by either the call:
   * <blockquote><pre>
   * src.connect(snk)</pre></blockquote>
   * or the call:
   * <blockquote><pre>
   * snk.connect(src)</pre></blockquote>
   * The two calls have the same effect.
   *
   * @param snk the piped reader to connect to.
   * @throws IOException if an I/O error occurs.
   */
  public synchronized void connect(PipedReader snk) throws IOException {
    if (snk == null) {
      throw new NullPointerException();
    } else if (sink != null || snk.connected) {
      throw new IOException("Already connected");
    } else if (snk.closedByReader || closed) {
      throw new IOException("Pipe closed");
    }

    sink = snk;
    snk.in = -1;
    snk.out = 0;
    snk.connected = true;
  }

  /**
   * Writes the specified <code>char</code> to the piped output stream.
   * If a thread was reading data characters from the connected piped input
   * stream, but the thread is no longer alive, then an
   * <code>IOException</code> is thrown.
   * <p>
   * Implements the <code>write</code> method of <code>Writer</code>.
   *
   * @param c the <code>char</code> to be written.
   * @throws IOException if the pipe is <a href=PipedOutputStream.html#BROKEN>
   * <code>broken</code></a>, {@link #connect(java.io.PipedReader) unconnected}, closed or an I/O
   * error occurs.
   */
  public void write(int c) throws IOException {
    if (sink == null) {
      throw new IOException("Pipe not connected");
    }
    sink.receive(c);
  }

  /**
   * Writes <code>len</code> characters from the specified character array
   * starting at offset <code>off</code> to this piped output stream.
   * This method blocks until all the characters are written to the output
   * stream.
   * If a thread was reading data characters from the connected piped input
   * stream, but the thread is no longer alive, then an
   * <code>IOException</code> is thrown.
   *
   * @param cbuf the data.
   * @param off the start offset in the data.
   * @param len the number of characters to write.
   * @throws IOException if the pipe is <a href=PipedOutputStream.html#BROKEN>
   * <code>broken</code></a>, {@link #connect(java.io.PipedReader) unconnected}, closed or an I/O
   * error occurs.
   */
  public void write(char cbuf[], int off, int len) throws IOException {
    if (sink == null) {
      throw new IOException("Pipe not connected");
    } else if ((off | len | (off + len) | (cbuf.length - (off + len))) < 0) {
      throw new IndexOutOfBoundsException();
    }
    sink.receive(cbuf, off, len);
  }

  /**
   * Flushes this output stream and forces any buffered output characters
   * to be written out.
   * This will notify any readers that characters are waiting in the pipe.
   *
   * @throws IOException if the pipe is closed, or an I/O error occurs.
   */
  public synchronized void flush() throws IOException {
    if (sink != null) {
      if (sink.closedByReader || closed) {
        throw new IOException("Pipe closed");
      }
      synchronized (sink) {
        sink.notifyAll();
      }
    }
  }

  /**
   * Closes this piped output stream and releases any system resources
   * associated with this stream. This stream may no longer be used for
   * writing characters.
   *
   * @throws IOException if an I/O error occurs.
   */
  public void close() throws IOException {
    closed = true;
    if (sink != null) {
      sink.receivedLast();
    }
  }
}
